Insulating-tube



IN V BE. v

Patented Apr. 3,1894.

M. R 'INSU' (No Model) Y UNTTED STATES PATENT OFFICE.

MINER ROBINSON, OF NEWTON, MASSACHUSETTS.

INSULATING-TUBE.

SPECIFICATION forming part of Letters Patent No.517,591, dated April 3,1894.

Application filed January 6, 1894.

To an whom it may concern.-

Be it known that I, MINER ROBINSON, of Newton, in the county ofMiddlesex and State of Massachusetts, have invented a new and usefulImprovement in Insulating-Tubes, of which the following, taken inconnection with the accompanying drawings, isaspecification.

My invention consists of animproved insulating tube for leading electricwires through timbers or other material, my object being to so constructthe tube that it is rigidly held in any position within the hole in thetimber previously made for it, and that it is always concentric with thehole, an air space being interposed between the outer surface of thetube and the inner surface of the hole for the purpose of more completeinsulation. To this end, the tube is provided with narrow ridgesarranged longitudinally in the manner hereinafter described.

Referring to the accompanying drawings Figure 1 shows in perspective thetube itself, and Fig. 2 is a sectional view showing the tube in placewithin the timber.

I make my improved tube preferably of glass or porcelain, or otherfire-proof non-absorbing insulating material.

A, is the body of the tube or the portion intended to pass through orrest within the hole I) in the timber B,and A is the enlarged head ofthe tube.

The portion A of the tube is provided with three or more ridges apresenting a narrow edge along the top and passing continuouslylengthwise of the tube from the head to a point at or near the outer endthereof.

A hole is bored in the timber B of a diameter slightly less than that ofa circle inclosing the ridges a, so that it is necessary to use someforce in driving the tube into the hole. The tube may be either drivenclear in so that the enlarged head rests against one surface of thetimber, or only partially so that acousiderable portion of the tube atthe head end projects beyond the timber, which latter position isdesirable forthe purpose of turning Saria1No.495.9ti3. (No model.)

a corner with the wire or changing its direction, thereby rendering anadditional insulator or fastening at that point unnecessary. In eithercase whether wholly or partially driven in, the tube is held very firmlyin the wood against any possibility of being turned around or changed inposition, or easily withdrawn.

Very high insulation resistance is secured by reason of the fact thatthe tube is in contact with the wood along the three ridges (to, a only,there being an air space between the main portion of the tube and theinner surface of the hole. This construction acts not only to greatlyincrease the insulation by reason of the small portion of the tube incontact with the wood, but also insures a quick drying out of the tubeand hole in case of wetting.

Although I have considered the use of the tube in connection with atimber, it is of course tobeunderstood that the tubeis equallyapplicable for use in brick work or other material in buildings.

1. A timber or other part of a wall or floor provided with the hole I)in combination with an insulating tube A having the longitudinal ridgesa throughout the entire length of the body of the tube whereby the tubeis firmly held concentrically in the hole with an insulating air spaceon all sides of the tube between it and the timber, substantially asdescribed.

2. An insulating tube A provided with longitudinal ridgesathroughouttheentire length of the body of the tube substantially as and for thepurposes described.

in testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, on this 24th day of November, A.D. 1893.

' MINER ROBINSON.

Witnesses:

ALBERT E. LEAOH, G. GUNTHER.

